#include <Eigen/SVD>
#include <iostream>
using namespace Eigen;
using namespace std;

float
inv_cond(const Ref<const MatrixXf>& a)
{
	const VectorXf sing_vals = a.jacobiSvd().singularValues();
	return sing_vals(sing_vals.size() - 1) / sing_vals(0);
}

int
main()
{
	Matrix4f m = Matrix4f::Random();
	cout << "matrix m:" << endl << m << endl << endl;
	cout << "inv_cond(m):          " << inv_cond(m) << endl;
	cout << "inv_cond(m(1:3,1:3)): " << inv_cond(m.topLeftCorner(3, 3)) << endl;
	cout << "inv_cond(m+I):        " << inv_cond(m + Matrix4f::Identity()) << endl;
}
